Add communication library for new RF Kill Board

[cbrxyz]

What needs to change?

We will need a library to work with the Light Tower board being developed by our electrical team (see uf-mil-electrical/NaviGator#2). This would include telling the board when we have switched between manual and autonomous control (as it should be able to derive when we are killed from the kill/relay board).

It looks like the inputs will be three high/low signals, so we should just be able to control the high/low statuses of the signals we are sending to the board to control it, but we will see!

How would this task be tested?

1. Ensure that our library is able to communicate with the new board.
2. Ensure that our library can't accidentally output two states at once.
3. Ensure that our library correctly responds to switching between autonomous/manual modes.